Tilt-up: An opportunity for the resurgence of craft

by Catherine Howlett | June 1, 2013 6:01 pm

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Photos © Ryan Gobuty/Gensler

by Mitch Bloomquist

As monumental-sized panels of concrete are lifted from their horizontal onsite casting position to a vertical element of the building enclosure, an impressive and unique craft is unveiled. In this industry, contractors are discovering inherent opportunities for a renewed focus on craftsmanship.

Definitions and origins of the word ‘craft’ refer to the ability to make or produce with care, skill, or ingenuity; the word also can mean strength and power. One would not normally think of a four-story office building as being ‘handcrafted;’ often, it is more accurate to say they are ‘assembled.’

While some components are made onsite, most come to the site and are combined according to the plans, specifications, and manufacturer’s instructions. With tilt-up concrete construction, contractors (sometimes general contractors, other times tilt-up installers) are working directly with and affecting the medium itself, creating one-of-a-kind works with each panel. This is also the case with cast-in-place concrete. However, tilt-up is uniquely positioned to maximize these opportunities for increased craft while maintaining a high level of efficiency and affordability.

To appreciate the inherent opportunities for craftsmanship afforded by tilt-up concrete construction, it is important to consider the well-recognized benefits of choosing the building system in the first place. One of the most common reasons for choosing tilt-up is the system’s ability to deliver on a fast schedule. While time most definitely is money, it is also directly related to quality, and because one of the greatest benefits of tilt-up is speed, there is more time to focus on it.

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Unexpected project solutions
With many other forms of construction, contractors are juggling the ordering, arrival, storage, installation, and finishing of a multitude of products. Each one of these steps or items creates opportunities for lost time and mistakes. With tilt-up, there are minimal products to coordinate, virtually no onsite storage needs, and, because of the time dedicated to meticulous planning, little opportunity for mistakes. The attention to detail and demand for precision does not stop after the planning stages—these upfront efforts create an onsite environment of accountability, knowledge, confidence, and focus.

This advantage of speed presents an opportunity to offer project solutions that may not seem possible to the owner. One case in point is a recent project for the University of California San Diego (UCSD). The school required office space quickly to accompany and support some major projects close to completion on their medical campus. A new cancer center was going up, and a shortage of space in other medical buildings meant it needed somewhere to put the additional support services.

UCSD initially planned on constructing a series of temporary buildings or trailers, but the senior director of healthcare project management for UCSD Facilities Design & Construction recommended considering tilt-up concrete construction. Having a great deal of experience with the system as an architect, he suggested a building using tilt-up could be constructed within the difficult budget and timeframe and they could potentially avoid investing time and money in a poor quality temporary fix.

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Tom Heffernan, the principal in charge of the project for Gensler, noted the request for proposals (RFP) issued by the university suggested tilt-up concrete construction as a good means of addressing the project requirements with its budget limitations and aggressive schedule.

“The team took this to heart and focused efforts on developing a tilt-up design that expressed the sculptural potential of site cast concrete,” he said. “UCSD and its surrounding community have a rich history of traditional cast-in-place concrete and we welcomed the challenge to use tilt-up methodology in an innovative way to design a new building that could hold its own among the other buildings on campus.”

Heffernan noted while speed was an important factor in the decision, there was more involved. The decision to use tilt-up concrete construction ultimately came down to the fact the method was able to provide a higher level of value to the university. Given a detailed RFP, a fixed budget, and straightforward campus requirements, C.W. Driver (general contractor) was able to estimate the costs of the interiors as well as the mechanical, electrical, and plumbing (MEP) systems with a high level of accuracy. What remained were the funds available for the skin, or façade, and structure.

“Within this budget, we could provide a conventional steel-framed building, but would only have enough budget left for a stucco or other low-cost cladding system,” explained Heffernan. “With the ‘triple-duty’ tilt-up system—cladding, lateral, and gravity system in one—we could provide a much higher level of quality to the university. A durable system with low maintenance requirements and, equally important, a system that afforded us powerful design opportunities.”

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Building art
UCSD’s team is not alone in realizing tilt-up’s potential in offering speed, economy, and design opportunities. However, in many ways, the Saint Louis Art Museum (SLAM) was in an opposite position, and still opted for the construction method. In this case, the museum had plenty of money and time. Why they chose to build with tilt-up had everything to do with the quality of construction they were looking for, the aesthetic they desired, as well as the monumental scale they had in mind.

The Saint Louis Art Museum, located in Forest Park, Missouri, is situated atop Art Hill overlooking the Grand Basin—the central gathering place for the 1904 World’s Fair. Designed by renowned American architect Cass Gilbert for the 1904 Louisiana Purchase Exposition, the museum’s original structure was the only building from the fair designed to be permanent. The building has undergone several modifications and various additions, with the latest meant to result in a more uniform look, providing modern accessibility and expanded capabilities.

• The 18,580-m² (200,000-sf) addition, designed by London architect David Chipperfield, provides for:
• new gallery space;
• fully accessible entrance;
• public space;
• restaurant overlooking Art Hill; and
• more than 300 parking spaces in a below-grade garage.

While fairly large, the addition has a relatively subtle exterior appearance. The above-grade, visible, portion of the building consists of large, clean expanses of glass and monumental planes of highly polished black concrete. Tilt-up was chosen because the methodology presented a unique opportunity to craft something ‘special’ that could not be done as efficiently or economically in any other way.

From the beginning, the design team desired a dark, monolithic concrete façade. With tilt-up, there was an opportunity to polish the panels horizontally, achieving a much higher-quality finish. Twenty-three panels were formed, cast, and finished on casting beds surrounding the structure. The 6.7-m (22-ft) tall panels range in width from 3.7 to 12.8 m (12 to 42 ft).

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Due to the slim margin for error and extremely tight tolerances, all panel edges were over-poured and cut to size. This process not only ensured the dimensional accuracy of the panels and a crisp clean edge, but it also reduced the time needed to polish the burdensome edges and returns. Additionally, by cutting the edges after the face of the panels had been polished, the polishing process could be taken to the edge without fear of chipping. The concrete mix design for the panels consists of various unique elements, including:

• Meramec Gravel, a natural river stone that comes from Missouri;
• glacial sand;
• black pigment; and
• Dresser Trap Rock, known as one of North America’s hardest rocks.

The process for getting these panels to this point took some hard work, a great deal of ingenuity, and skilled craft.

Julie Bauer, the lead design architect for David Chipperfield Architects on the project, was amazed at the level of craft being accomplished on these panels. She said one of the most interesting aspects of the process was the construction crew was seemingly inventing tools and methods on the spot for troubleshooting areas and getting the panels to a state of which they could be proud. Every square inch of each panel was cared for and worked to perfection.

The director of the museum elaborated on the concept of going with these relatively enormous handcrafted panels over, say, granite tile. He said instead of being made up of small panels, the project was to be made up of massive, monumental panels appropriate to a public building that will be here for a century more.

Not only possible, but practical
More and more designers and contractors are discovering complex forms and rich textures are not only possible with tilt-up, they are actually practical. Located in a small beach community just a short drive from Charleston, North Carolina’s historic district is a simple church with a unique finish. The contractor said site-built tilt-up panels was chosen as the delivery method for a substantial addition because it was the only accessible way to produce the desired results in an economically feasible manner. The goal was to replicate a tabby or tabby stucco finish.

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The term ‘tabby’ refers to a centuries-old, southern U.S. coastal building material composed of equal parts of homemade lime, sand, oyster shells, and water. Once dried, they would then place a surface layer of stucco over the wall to protect the finished product. Over time, the recipe has been modified to include portland cement. This variation exposes the shell and foregoes the stucco, which is not an entirely accurate recreation (which is common), but a weathered take on the historic material.

To adopt the technique for tilt-up, the team brainstormed and tested mockup panels. The solution consisted of hand-stacking the oyster shells in a 9.5-mm (3⁄8-in.) thick sand-bed and using white cement to bond the shells in a textured layer, and then constructing the structural layer. The best part of all of this is the congregation was invited to participate in the placing of the shells. Since each hand had its unique way of setting a shell, the entire group of workers shifted and traded positions at timed intervals throughout the process to avoid large areas looking different from others. The result is a uniquely beautiful texture.

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Maximizing concrete’s benefits
As a building material with measurable and adjustable flowability, concrete can be cast into virtually any shape; this yields an infinite number of project solutions. Tilt-up permits the creation of massive vertical form from a material that easily flows across the form created horizontally. During the forming stage, the tilt-up contractor is basically creating a mold. From the finishing of the casting slab to the caulking of the form joints, the attention to detail and high quality is important.

This level of craft was evidenced by the crew that constructed the Korean War Veterans Memorial in Kansas City, Missouri. The project consists of three panels—two for the wall and one for the roof. The overall shape of each was a parallelogram with 45-degree angles. However, the two faces of the panel were designed to be misaligned. At the bottom of the panel, the faces were offset 203 mm (8 in.) in one direction and at the top 203 mm in the other direction. The edge of the panel in between the two faces was to be triangulated, creating a faceted edge. All this was done within the 203-mm tall edge forming; the faces of the panels were flat.

There are two specific aspects or details of this project that need further explanation. The first is the way the edges were formed. Each one is bent along an axis shifting in orientation. The forming of this condition was very interesting. To complicate things further, this bend was interrupted by several different reveal strips and panel recesses. This simple technique added drama and depth to the form not traditionally expected from flat panels.

The second detail of this project that took advantage of the fluidity of concrete is on the exterior of the memorial where two large images, one on the outside face of each wall, are cast into the concrete. Grooves of varying depths and widths affect light cast on the structure to reveal the imagery. To create the required formliners, photographic images were carved into a wooden ‘tool’ or mold using a computer numerical control (CNC) milling machine. Each mold was then used to create the elastomeric liner.

Another huge advantage of building with tilt-up is the ability to work horizontally. Since tilt-up panels are formed and cast horizontally, there are endless opportunities for unique forms and innovative textures (as discussed in the aforementioned museum project).

The ability to easily deliver form creativity is one of many attributes of tilt-up construction contributing to the resurgence of craft. The form of a tilt-up panel can be manipulated in plan, elevation, or both. Curved, angled, and shaped panels are regularly used and offer designers flexibility not economically practical on most projects.

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Delivering on expectations
As these techniques become more common, it is important there be a tool for communicating expectations. Later this year, the Tilt-Up Concrete Association (TCA) is publishing an updated guideline specification. The new document intends to aid in the communication between project team members, serving as a script for the working relationship between the contractor and the owner’s design team. After all, this team sets the stage for evaluation of the work with a defined set of acceptance standards.

According to Jim Baty, TCA technical director, while specifications do not limit the level of craftsmanship, they do establish the benchmark for expectations.

“The tilt-up industry continues to promote a high level of standard for this benchmark through a packaged guideline specification,” he explained. “The new update to this document that will be issued in the second quarter of 2013 will reaffirm this attention to quality and craftsmanship through minimum expectation language recommended by the professionals found throughout the Tilt-Up Concrete Association.”

Conclusion
Construction is often seen as the necessary means to an end. However, it is imperative design professionals take time to celebrate the tangible ways in which construction plays the most significant role, once again, in the way buildings are achieved. The rate at which the quality of the design and construction of tilt-up buildings is improving is astonishing. Each year, there are projects breaking new ground with a unique finish, an unbelievable form, incredible size, incredible speed, or new applications. Craftsmanship and pride in the industry continues to soar, as tilt-up concrete construction becomes the answer for more projects.

 

Mitch Bloomquist is a staff member at the Tilt-Up Concrete Association (TCA), the international nonprofit trade association for the global tilt-up concrete construction industry. He earned his master’s degree in architecture from Washington University (Saint Louis, Missouri). Bloomquist contributes to, and oversees, production of multiple publications, including Tilt-Up Today, The Construction of Tilt-Up, and The Architecture of Tilt-Up. Currently, he is working with TCA members on a third publication, The Engineering of Tilt-Up. He serves as the staff liaison to TCA’s safety, promotions, and awards committees, and oversees the organization’s Tilt-Up Achievement Awards Program, Student Design Competition, and Safety Awards Program. Bloomquist was involved in many major projects as an associate with Novak Design Group, an architectural firm in Cedar Rapids, Iowa. He can be contacted via e-mail at mbloomquist@tilt-up.org[9].

Source URL: https://www.constructionspecifier.com/tilt-up-an-opportunity-for-the-resurgence-of-craft/

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